Plastic closures have become economically desirable in the beverage bottling industry. However, standard glass bottles have reliable dimensional tolerances for outside diameter of finish only, and do not have reliable tolerances for inside diameters or for the top surface of the finish. When closures are designed to seal on the inside or top of the bottle, the bottles cannot be made with the degree of precision required for a durable, high pressure plastic-to-glass seal. Also, closures employing only a top seal are subject to failure caused by internal pressure lifting the cap and breaking the seal. A final consideration is that the cap, while it must seal high pressures reliably during storage and handling, must be easily removable by the consumer.